INDUSTRIAL AND EKGINEERING CHEMISTRY
7%
(3) Erasmus. Paul, “Uber die Bildung und den chemischen Bau der Kohlen”, Stuttgart, Verlag von Ferdinand Enke, 1938. (4) Fisher, C. H., IND.ENG.CHEM.,Anal. Ed., 10, 374-7 (1938). ( 5 ) Fisher, C. H., and Eisner, A., IND.ENG. CREM.,29, 1371 (19371. (6) Fisher, C. H., Sprunk, G. C., Eisner, A., Clarke, L., and Storch, H. H., Ibid., 31, 190 (1939). (7) Ibid., 31, 1155 (1939). (’ ((8) Fisher, C. H., Sprunk, G. C . , Eisner, A,, Clarke, L., and Storch, H. H., Fuel, 18, 132 (1939). (9) Ibid., 18, 196 (1939). (10) Francis, W., J. I n s t . Fuel, 6 , 301-8 (1933). (11) Gordon, K., T r a n s . I n s t . M i n i n g Engrs. (London), 82, P t . 4, 348-63 (1931). (12) Graham, J. G., and Skinner, D. G., J. SOC.Chem. I n d . , 48,129T (1929). (13) Hirst, L. L., et al., IND.ENG.CHEW,31, 869 (1939). ~I
VOL. 32, NO. 1
Horton, L., Williams, F. A,, and King, J. G., Dept. Sci. Ind. Research (Brit.), Fuel Research Tech. Paper 42 (1935). Hovers, T., Koopmans, H., and Pieters, H. A. J., F u e l , 15, 233
\-_-_,.
I1 RR6)
(16) Petrick, A. J., Gaigher, B., and Groenewoud, P., J. Chem. M e t . M i n i n g SOC.S . A f r i c a , 38, 122-4 (1937). (17) Seyler, C . A., Fuel, 17, 177, 200, 235 (1938). (18) Shatwell, H. G., and Graham, J. I., Ibid., 4, 25, 75, 127, 252 (1926). (19) Storch, H. H., I N D .EXG.CHEM.,29, 1367 (1937). (20) Thiessen, R., rept. presented before Fuel Engrs. of Appalachian Coals, Jan., 1937. (21) Wright, C. C., and Gauger, A. W.,Am. Mining Congr., Coal Mines Mechanization, Yearbook, pp. 381-3 (1937). PRESENTED before t h e Division of Gas and Fuel Chemistry a t the 97th Meeting of the American Chemical Society, Baltimore, >Id. Published by permission of t h e Director, U. S. Bureau of Mines (not subject t o copyright).
Evaluation of Nitrocellulose Lacquer Solvents A Study of Hydrocarbon Diluents by the ConstantViscosity Procedure V. W. WARE AND W. M. BRUNER E. I. du Pont de Nemours & Company, Inc., Wilmington, Del.
HE first paper of this series (9) described in detail the
T
constant viscosity procedure for the evaluation of the solvent strength of nitrocellulose lacquer solvents. By this method a single value may be assigned to the combined viscosity characteristics and hydrocarbon acceptance of a solvent in such a way that a separate study of the two is eliminated, and it may be used, in turn, to relate this combined solvency value to the cost of application. This method of evaluation has been applied to a number of commercially available esters (ethyl acetate, ethyl propionate, isobutyl acetate, wbutyl acetate, isobutyl propionate, and Pentacetate) in their reaction to toluene dilution (IO). I t gives a complete picture of the reaction of nitrocellulose lacquer solvents to hydrocarbon addition throughout the entire range of dilution and affords a means of obtaining an accurate comparison of their solvent action a t the viscosity most applicable to the problem a t hand. The “dilution ratio” of a nitrocellulose solvent has been defined (1) as expressing the limit of tolerance of a solvent for a nonsolvent; but as Gardner (6) points out, the end points are rather indefinite, and considerable experience is necessary to be able to check the results. Doolittle (3) made worthwhile advances in defining the limits and the conditions under which dilution ratios should be determined, but they still remain an unsatisfactory and uninformative type of analytical procedure. Moreover, Stewart (8) reported that the inclusion of resin in the experimental formulation tends to make the end point still more difficult to check than in the case of
solutions of nitrocellulose alone. Dilution ratio is used in evaluation of the activity of diluents as well as solvents, and from the above considerations it is obvious why this method is still more unsatisfactory in diluent evaluation than in the evaluation of solvents. This also indicates why the constant viscosity procedure, which eliminates the dilution ratio completely and measures the action of the diluent by means of changes in the viscosity or in the solids which will dissolve a t a given viscosity, offers advantages for this purpose. The viscosity and hydrocarbon tolerance of a solvent are but two of the several important factors which contribute to the value of the material, and it is not the intention of this series of papers to overemphasize that importance. The intent is, rather, to make available to the industry certain pertinent data that give a clearer view of the subject and to point out the more obvious and logical deductions from these data. Stated briefly, the constant viscosity procedure for measuring the power of solvent and solvent-diluent mixtures to dissolve nitrocellulose involves viscosity determinations of nitrocellulose solutions in three or more concentrations in the range of spray viscosity. From these data curves are drawn by plotting viscosity against weight of nitrocellulose per 100 cc. of base lacquer. The exact solids concentration a t any viscosity within the chosen range may be obtained from the curve, and curves may be set up from experimental data in this way for any number of solvent-diluent mixtures. These values for nitrocellulose concentration a t any chosen standard viscosity are in themselves an accurate means of comparing the solvent strengths of two or more solvent mixtures since they combine in one set of values all of the information which previously has required both dilution ratio and viscosity determinations. However, the usefulness of the data may be extended much further; by plotting the solvent-diluent composition against nitrocellulose or solids concentration, as obtained from the first set of curves, a second curve may be obtained (9, IO) from which the ratio of solvent t o diluent which will dissolve a given amount of nitrocellulose a t that viscosity may be read. Then, knowing the apparent value of the diluent and of the solvent in use as standards, the comparative value of the solvent or diluent under test may be established.
JANUARY, 1940
IKDUSTRIAL AND ENGINEERING CHEMISTRY
Data obtained by the constant viscosity procedure for nitrocellulose solvent evaluation are presented for three types of hydrocarbon diluent: pure coal tar (toluene), pure aliphatic (gasoline), and mixed aromatic-aliphatic or so-called high-solvency naphtha. These diluents have been studied in conjunction with four commercially available esters: isobutyl acetate (90 per cent), n-butyl acetate (90 per cent), isobutyl propionate (80 per cent), and Pentacetate (87 per cent). The comparisons were made in the presence of nitrocellulose alone and also with a 2 to 1 mixture of nitrocellulose and resin. The value as a diluent decreases in the order, toluene, high-solvency naphtha, gasoline; this decrease is considerably greater with nitrocelluloseresin mixtures than i t is when the nitrocellulose composes the entire make-up of the solids ingredients, but in no case is it enough to be of any great practical value until a dilution beyond 20 per cent is used. The complete similarity and equivalency of isobutyl acetate and n-butyl acetate, as concerns their solvency characteristics and diluent acceptance with the three types of hydrocarbons throughout the entire dilution range at spray viscosity, is demonstrated. This equivalency is not noticeably affected by the presence of resin in the formulation. The superior solvent strength of isobutyl propionate as the high-boiling ingredient of nitrocellulose lacquers is shown.
While previous communications have dealt primarily with the constant viscosity procedure as a means of assigning a value to the solvent strength of the active solvent constituents of a lacquer, i t is the object of this paper t o show how the method may be applied advantageously to the evaluation of diluents as well. For this purpose one each of the three general types of hydrocarbon diluent now used in commercial lacquers was chosen-pure aromatic, pure aliphatic or gasoline type naphtha, and the mixed aromatic-aliphatic or socalled high solvency naphtha. Commercial 2” C. toluene is used in the first case. A commercial naphtha with a distillation range of 90-130” C. is used in exemplifying the pure aliphatic type; it will be referred to hereafter simply as gasoline. The mixed aromatic-aliphatic naphtha used is a commercial material with a distillation range of 95-132’ C., containing approximately 30 per cent aromatics; i t will be referred to as H. S. naphtha. Each of these naphthas evaporates a t approximately the same rate as toluene. The high-solvency naphtha type of diluent has been described (7) as being far superior to mineral spirits and approaching in solvent power and compatibility the coal t a r solvents. Since these diluents are being used rather extensively in lacquer formulations, i t seemed appropriate that they be examined in the light of the constant viscosity procedure. It has been shown (4)t h a t both the solvent balance and solvent action are influenced by the type and concentration of the nonvolatile portion. Therefore it seemed likely that, whereas the pure aliphatic naphtha and the mixed naphtha may show similar dilution effects on nitrocellulose alone, the differences may be much more pronounced in the presence of certain resins because of the selective action of the aromatic portion in the one case. For this reason and in order t o avoid any possibility of misinterpretation, it seemed advisable to
79
compare the action of these diluents, not only on nitrocellulose alone, but on mixtures of nitrocellulose and resin as well. Hence a series of tests is included which is based upon a mixture of nitrocellulose and resin in proportions of 2 to 1; this approaches the composition often used in commercial lacquers. The resin was an alkyd modified with a nondrying oil. Obviously, the reaction of other resinous materials in the presence of nitrocellulose will not be the same as this particular one; this information is furnished in order t o emphasize the importance of studying the effect of the resin, as well as the nitrocellulose, on solvent behavior.
Experimental Procedure The experimental details are identical with those described in a previous paper (9). Browne ( 2 ) states, in connection with paints, that “most of the useful properties of paint are determined at least to a first approximation by the proportions of ingredients by volume: volume, not weight, governs the area coverable with a film of suitable thickness, governs the concentration of opaque pigments in the film necessary to give the desired hiding power, and the concentration and proportions of total solids required for good consistency in application and for optimum durability.” I n the belief that this applied just as well to nitrocellulose lacquers and enamels and that the conventional formula in percentages by weight has a tendency to obscure certain relations because of the great variation in the specific gravity of the various ingredients, the work has been continued on a volume rather than a weight basis. Hence all solids concentrations are expressed as grams per 100 cc. of solution, and all solvent-diluent ratios refer to percentage by volume. Dry, l/a-second nitrocellulose from the same lot as that in the experiments previously described (9, 10) was used throughout, and the same accuracy in weighing and volume measurements was maintained. All viscosity measurements were made on the Parlin No. 7 cup (5) at 25” C. * 0.1’. Viscosity values were obtained for three or more solids concentrations with each mixture, and the quantity of solids was chosen so that these values cover the entire range of spray viscosity. All samples were tumbled at an identical rate for 24 hours to ensure complete solution. The recorded viscosity in seconds for the three or more solids concentrations with each solvent-diluent mixture is plotted against grams of nitrocellulose, and thc curves so obtained are shown. I n the previous articles (9, 10) tables were included to show the m o u n t of nitrocellulose which dissolved at certain standard viscosity readings, but for purposes of brevity they are not given here. The curves shown indicate graphically the behavior of a solvent mixture; the derived values are most useful in those cases where it seems necessary to calculate the ultimate comparative cost values of solvents or diluents. The diluents used in this work were commercial 2’ toluene, the high-solvency naphtha offered by the Union Oil Company of California under the name of “Solvent #8”, and “Hayway Naphtha $55’’ from the Standard Oil Company of New Jersey. The n-butyl and isobutyl acetates possessed a saponification value of approximately 90 per cent, the isobutyl propionate 80 per cent, and the Pentacetate 87 per cent. The remainder in each case was composed of the alcohol from which the ester was derived. Isobutyl propionate with an alcohol content of 20 per cent possesses optimum properties as far as the viscosity and hydrocarbon acceptance of this ester are concerned, hence the choice of this strength for the work. The other three esters are offered commercially a t approximately the alcohol content used in these experiments, hut these may or may not represent the mixture of optimum solvent properties.
Viscosity Data The experimental viscosity values for solutions of nitrocellulose in 90 per cent isobutyl acetate at various dilutions with toluene, high-solvency naphtha, and gasoline are shown in Table IA. No values are given for 40.60 dilution with gasoline because a t this point nitrocellulose is incompletely soluble in the mixture. Table IB contains the experimental values for 90 per cent n-butyl acetate with the three hydrocarbons. Here again i t
INDUSTRIAL AND ENGINEERING CHEMISTRY
80
was not possible to obtain readings a t a gasoline dilution of 60 per cent because of the insolubility of nitrocellulose in the composition. I n Table IC the experimental values for 80 per cent isobutyl propionate diluted with the three hydrocarbon diluents are shown. A comparison of the values for toluene dilution here with those given for the 87 and 99 per cent ester in a previous communication (IO) will indicate the striking increase in solvent strength obtained with small increases in the alcohol content of this ester. Dilution of 80 per cent isobutyl propionate to 40:GO with either of the hydrocarbons results in incomplete solubility of the nitrocellulose, although clear solutions are obtained in each case a t 50:50 dilution. Table ID gives the corresponding information for 87 per cent Pentacetate, which accepts dilution to about the same extent as the propionate, although the viscosities with the latter are considerably lower.
, TABLE I. VISCOSITY-NITROCELLULOSE CONTENT OF SOLUTIONS AT VARIOUSHYDROCARBON DILUTIONS Solvent: Diluent Ratio
-Nitrocellulose/lOO Cc. Base Lacquer"6 grams 7 g r a m 8grame 9grama l o g r a m s Sffi. Seo. Sec. Sa. Sffi. A. Isobutyl Acetate Solutions 71.0 1oo:o 42.0 54.0 None 41.5 55.6 78.5 80:20 Toluene 45.0 57.7 78.7 37.2 80:20 H. S. naphtha 44.3 56.5 77.3 37.5 80 :20 Gasoline 62.7 89.7 48.4 38.8 60:40 Toluene 72.7 103.3 40.0 53.0 60:40 H. S. ,naphtha 79.3 42.6 57.0 35.0 60:40 Gasoline 71.9 50:50 39.0 52.3 Toluene 94.2 60:50 35.4 45.0 64.2 H. S. naphtha 50:50 40.4 64.1 81.0 Gasoline 101.0 40:60 38.0 46.3 67.3 Toluene ... 40:60 39.6 62.0 122.0 H.9. naphtha B. n-Butyl Acetate Solutions 52.5 67.2 1oo:o 41.7 None 54.9 71.4 42.0 80:20 Toluene 76.5 57.7 80:20 36.7 45.3 H. 5. naphtha 56.7 76.4 80:20 36.8 45.1 Gasoline 62.1 86.0 38.0 47.3 60:40 Toluene 73.2 60:40 40.1 52.2 H. 9. naphtha 75.1 60:40 34.0 41.4 52.9 Gasoline 70.5 50:50 ,.. 40.0 51.6 T o Iu e n e 95.7 50:50 35.0 46.0 64.1 H. S. naphtha ... 50:50 37.0 48.9 70.0 Gasoline 96.7 40:60 36.0 46.0 63.3 Toluene 40:60 41.4 66.2 113.3 H. S. naphtha C. Isobutyl Propionate Solutions 61.2 82.5 1oo:o 38.5 46.2 None 65.6 85.7 39.8 49.7 80:ZO Toluene 96.9 66.2 80:20 ... 39.0 50 5 H. S. naphtha 73.7 80:20 34.6 41.3 50.8 Gasoline 68.2 60:40 ... 40.1 50.0 Toluene 91.5 60:40 36.0 44.7 60.2 H. S. naphtha 60:40 38.0 51.8 68.2 Gasoline 84.4 50:50 35.2 42.1 58.4 Toluene ... 50:50 41.6 61.3 93.8 H. S. naphtha 50:50 47.3s 75.3 Gasoline D . Pentacetate Solutions 72.3 40.3 53.0 1oo:o None 75.1 40.5 55.5 80:20 ... 43.0 Toluene 80.0 57.3 80:20 35.3 H. S. naphtha ... 42.4 56.0 80:20 35.4 Gasoline 87.8 45.1 60.5 60:40 34.8 Toluene ... 46.8 71.7 60:40 36.2 H. S. naphtha 52.4 79.2 60:40 39.4 Gasoline ... 48.6 67.5 50:50 38.0 Toluene ... 64.8 97.0 50:50 42.9 H. S. naphtha ... ... 50:50 5O.Oc 78.9 Gasoline 0 Viscosity in No. 7 cup a t 25" C. b Viscosity at 5 grams, 37.2 seconds. C Viscosity a t 5 grams, 38.1 seconds. Diluent
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VOL. 32, KO. 1
to multiply the weights of nitrocellulose used by the factor 1.5 in order to study the viscosity variation on the basis of total solids. When the contents of Table IIA are compared with those of Table IA for nitrocellulose alone, the increase in viscosity when the solids are increased 50 per cent by means of resin is seen to be relatively small. Some of this increase is due to the fact that a certain amount of the solvent mixture has been replaced by an equal volume of resin. TABLE11. VISCOSITY-NITROCELLULOSE CONTENT OF ISOBUTYL ACETATEAT VARIOUSHYDROCARBON DILUTIONB WITH A NITROCELLULOSE: RESINRATIOOF 2: 1 Solvent: Diluent Ratio
-Nitrocellulose/lOO Cc. Base Lacquera5 grams 6 grama 7 grams 8 grams 9 gramab Sec. SCC. Sffi. Sea. Sic. A. Isobutyl Acetate None 1oo:o 42.4 53.0 72.3 Toluene 80 :20 35.6 43 3 54 3 76 7 H.S. naphtha 80:20 38 1 44 6 60 2 87 8 Gasoline 80 :20 39.2 46 5 66 0 94.6 Toluene 60 : 40 36.9 46.8 69.5 H.S. naphtha 60:40 40.8 54.6 85.0 Gasoline 60:40 36.0 48.7 72.8 Toluene 50:50 39.3 51.4 75.8 H.8. naphtha 50:50 37.3 51.2 72.1 Gasoline 50:50 Not soluble Toluene 40:60 34.8 44.0 68.3 H. S. naphtha 40;60 Not soluble B. n-Butyl Acetate None 1oo:o 41.5 51.9 70.3 Toluene s0:20 ... 41.4 54.2 73.2 H.9. naphtha 80:20 42.2 56.4 78.9 Gasoline 80:20 35.8 43.0 57.2 81.7 Toluene 60:40 36.5 46.7 65.6 94.3 H.S. naphtha 60:40 39.5 53.6 78.5 Gasoline 60:40 33.8 45.3 65.0 ... ... Toluene 50 :50 39.0 50.3 73.2 H.9.naphtha 50:50 35.7 48.7 71.6 Gasoline 50:50 Not soluble Toluene 40:60 35.0 43.8 66.5 H.9. naphtha 40:60 Not soluble 4 Visaosity in No. 7 cup a t 2 5' C. b T o obtain corresponding total solids, multiply by 1.5. Diluent
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Table IIB gives similar information for n-butyl acetate with the three diluents and the nitrocellulose-resin mixture. I n the case of both of these esters the nitrocellulose-resin mixture will not dissolve a t 50 per cent gasoline dilution or a t 60 per cent high-solvency naphtha dilution. Toluene, however, maintains its excellent diluent properties a t 60 per cent dilution although there is a noticeable viscosity increase with the addition of the resin over t h a t observed with the nitrocellulose alone.
Curves Derived from Data The experimental viscosity values in the tables are plotted against nitrocellulose concentration. Figure 1 sbows the curves for the four esters with nitrocellulose alone and the two
...
Table IIA includes the experimental viscosity values for isobutyl acetate with the three types of hydrocarbon; the solids, instead of being composed of nitrocellulose alone, were made up on a weight basis of 2 parts of nitrocellulose to 1part of resin. For comparative purposes the practice of expressing the results on the bask of grams of nitrocellulose per 100 CC. of base lacquer has been continued, and it becomes necessary
FIQURE 1. VISCOSITY-NITROCELLULOSE CONTENT CURVES FOR 100 PARTS SOLVENT 1. Isobutyl acetate (90 per cent) 2 n-Butyl acetate (90 per cent) 3. Isobutyl propionate (80 per cent) 4. Pentacetate (87 per cent) 5. Isobutyl acetate (nitrocellulose: r e s h 6. n-Butyl acetate (nitrocellu1ose:resln
--
2:1) 2: 1)
INDUSTRIAL AND ENGINEERING CHEMISTRY
JANUARY, 1940
81
70 65
60
55
50 45
40 6
7
8
9
IO
6
7
8
G NITROCELLULOSE PER 100 CC BASE LACQLCR (MULTIPLY BY I 5 FCR G OF TOTAL SCUDS)
FIGURB~ 3. VISCOSITY-NITROCELLULOSE CONTENT CURVES FOR I S O B U T Y L AND +BUTYLACETATE AT 40:60 DILUTION 1. Isobutyl acetate-toluene 2. Isobutyl acetate-H. S. naphtha 3. n-Buti1 acetate-toluene 4. %-Butyl acetate-H. S. naphths
6
7
G N T R O C ~ L - U L C S E PER
8
103 cc
9
IO
BASE LACQUER
FIQURE 2. VISCOSITY-NITROCELLCLOSE CONTENTCURVES A , 8O:ZO dilution: B , 00:40: C. 60:60. 8 . Iaobutyl propionate-H. S. naphllia 9. I R O ~ I I propionate-gasoline I~I 10. Pentnrel ate-t oluene 1 1 . Pentacetate-H. S. naphtha 12. Pentaoetate-gasoline
butyl acetates with the nitrocellulose-resin composition, all in the absence of any diluent. Although viscosity values for the undiluted solvent are of little practical value from the standpoint of lacquer solvent evaluation, they are still widely used i n the inclustry for evaluative purpnses, and considerable emphasis is often placed upon the viscosity of the nitrocellulose solution in t h e solvcnt alone when comparisons are being made. The curves show the small differences which exist between the butyl acetates antl indicate that these differences are practically the same whether or not resin is present in the formulation.
Figure 2A shows the reaction of these four esters to the three types of diluent a t 20 per cent dilution. The curves indicate that, in the absence of resin or other material which might complicate the relation, there is little to be gained by the use of the aromatic over the pure aliphatic type hydrocarbon. The first six curves for the two butyl acetates show the almost complete coincidence of the two esters with gasoline and high-solvency naphtha, with toluene offering a slight advantage in each case. Isobutyl propionate lies about midway between Pentacetate and the butyl acetates in solvent action a t this dilution. Figure 2B gives the viscosity-nitrocellulose content curves for 40 per cent dilution. The differences between the three diluents are becoming more noticeable, with those between the esters (particularly between n-butyl and isobutyl acetate) remaining but slightly changed over those a t lesser dilutions. Curves 1 and 4 for toluene dilution, 2 and 5 for high-solvency naphtha dilution, and 3 and 6 for gasoline dilution bear out the conclusion that for all practical purposes the butyl acetates possess the same solvency cliaracteristics with any given hydrocarbon diluent. The most striking observation in this case is that concerning isobutyl propionate which has shown a remarkable increase in solvent strength relative to the other esters. This is especially true with toluene dilution (curve 7) which is but slightly inferior to the solvency of the butyl acetates. The reaction of isobutyl propionate to high solvency naphtha dilution is also extremely good; it is slightly lower than that of isobutyl acetate antl almost identical with that of Pentacetate and toluene. With gasoline, however, the isobutyl propionate has shown a relative decrease in activity and is only slightly superior to Pentacetate. A t 50.50 dilution (Figure 2C) isobutyl and n-butyl acetate remain almost identical in their reaction to toluene and highsolvency naphtha addition. Although the difference is somewhat greater with gasoline, it is never more than 5 per cent based on solids in solution. Isobutyl propionate with toluene continues to show up extremely wcll, but the curves for both the high-solvency naphtha and gasoline with this ester are somewhat closer to those of Pentacetate with the same diluents. Dilution with 60 per cent hydrocarbon is beyond the limite of compatibility for both isobutyl propionate and Pentacetate and also those of the butyl acetates with gasoline. Figure 3, therefore, shows only the curves for isobutyl and n-
INDUSTRIAL AND ENGINEERING CHEMISTRY
82
I
7
6
8
9
VOL. 32. NO. 1
1
I
5 6 G. NITROCELLULOSE-PER 100 cc. 7 (MULTIPLY BY
I
BASE LACQUERR
v
1.5 FOR G. OF TOTAL SOLIDS)
FIGURE 5. VISCOSITY-NITROCELLULOSE CONTENT CURVES FOR ISOBUTYL AND %BUTYLACETATE AT 50:50 AND 40:60 DILUTION,WITH A NITROCELLULOSE: RESINRATIOOF 2 : l 1. Isobutyl acetate-toluene (50: 50) 2 Isobutyl a c e t a t e H S. naphtha 50 50) 3: Isobutyl acetate-tdluene (40:60\ :
4. n-Butyl acetate-toluene (50:50)
5 . n-Butyl a c e t a t e H . S. naphtha (50:50) 6. n-Butyl acetate-toluene (40: 60)
I
1
5
6
I
7
8
G. NITROCELLULOSE PER 100 CC BASE LACQUER (MULTIPLY
BY I 5 FOR
t OF TOTAL SOLIDS)
FIGURE 4. VISCOSITY-NITROCELLULOSE CONTENT CURVES FOR ISOBUTYL A N D n-BuTYL ACETATEAT 80:20 (A) AND 60:40 (B) DILUTIONS WITH A NITROCELLULOSE:RESIN RATIOOF 2: 1 1. Iaobutyl acetate-toluene
2. Isobutyl acetateH. S. naphtha
3. Isobutyl acetate-gasoline 4. n-Butyl acetate-toluene 5. n-Butyl acetate-H. S. naphtha 6. n-Butyl acetate-gasoline
butyl acetate with toluene and high-solvency naphtha at this dilution. Figure 4A is concerned with the reaction of isobutyl acetate and a-butyl acetate to 20 per cent hydrocarbon dilution in the presence of a 2 to 1mixture of nitrocellulose and resin. At this low dilution there is only a small viscosity increase over that observed with the nitrocellulose alone, as the toluene is replaced by high-solvency naphtha and then by gasoline. The two esters possess essentially the same solvency with each diluent. The weight values given in Figures 4 and 5 refer only to the amount of nitrocellulose present in the mixtures, and these values should be multiplied by the factor 1.5 to obtain total solids. Also, in comparing these values with those for nitrocellulose alone, it should be kept in mind that a volume of the solvenMiluent mixture equal to the volume of the resin has been replaced by resin in each case. At the dilution of 40 per cent (Figure 4 B ) the effect of the presence of resin in the formulation becomes marked. This is particularly true at the higher solids contents and results in curves with a much steeper slope than occurs a t the same dilution (Figure 2A) in the absence of any resin. It is interesting to note that in practically all of these cases the effect of toluene upon the solvent action of isobutyl acetate and n-butyl
acetate is practically identical, that the curves for high-solvency naphtha with the two esters are in general somewhat farther apart than those for toluene, and that the gasoline dilution curves show a still wider divergency. This is illustrated with especial clarity in Figure 4B. However, in no case is the difference, even with gasoline, greater than 5 per cent when calculated on the amount of solids in the two compositions at a given viscosity. Figure 5 gives the viscosity-nitrocellulose content curves for the two butyl acetates at 50:50 dilution with toluene and high-solvency naphtha. This is beyond the limits of compatibility with straight gasoline. The curves for 40:60 dilution with toluene, which is beyond the miscibility range for both gasoline and high-solvency naphtha, are also included. Further studies now in progress demonstrate the utility of the constant viscosity procedure, not only for measuring the activating effect of various alcohols on nitrocellulose solvents, but for examining in a practical way the use of alcohols as lacquer diluents. This method has also been applied t o the examination of the hydrocarbon activation of certain lacquer solvents which show this property in a surprising degree and to a much greater extent than occurs in the activation of esters by means of alcohols.
Literature Cited (1) Brown, B. K..a n d Bogin, Charles. IND.ENQ.CEBM.,19, 968 (1927). (2) Browne, F.L.,Ibid., 29, 1020 (1937). (3) Doolittle, A. X., Smith, R. E., a n d Penn, G . R.. Paint Oil Chsm. Rev., 99, 26 ( M a y 13. 1937). (4) Dorsch, J. B., and Stewart, J. K., IND. ENQ.CHEM.,30, 326 (1938). (6) Gardner, H.A., “Physical and Chemical Examination of Paints, Varnishes. Lacquers and Colors”, 8th ed., p. 585 (1937). (6) Ibid., p. 1088. (7) Lazar, A.,IND.ENQ.CHFM.,28. 659 (1936). (8) . . Stewart, J. K.. Dorsch, J. B.. a n d Hopper,C. B., Ibid.. 29, 902 (1937). (9) Ware, V. W.,and Teeters, W . O., Ibid., 31, 783 (1939). (10) Ibid., 31, 1118 (1939). PRESBNTED before the Division of Paint and Varnish Chemistry at the 97th Meeting of the American Chemical Society, Baltimore, Md.
